What is VDEP?

VDEP, or Vegetation Departure is an ecosystem condition metric that compares modeled historical amounts (reference) of ecosystem succession classes (a.k.a. “seral states” or “developmental classes”) to current. The final output is a single number per ecosystem that ranges from 0 to 100. When you download VDEP data from LANDFIRE (https://www.landfire.gov/vdep.php), this is what you get-that final number (VDEP math is pretty simple as in example table below for one imaginary unnamed ecosystem. VDEP is 48 in the example).


When you map the VDEP data, you are essentially mapping 0 to 100 for all ecosystems within the area of interest such in this map of VDEP for the coterminous United States.



Since LANDFIRE delivers VDEP, why do we need to do anything?

While interesting and useful for general assessments, the downloaded VDEP data does not tell you which succession classes are over or under represented-you only get the 48 in the example table above. To get at over and under representation we need to get the amounts of each succession class for the Biophysical Settings (ecosystems) that occur within our area of interest.

The figure below (from Swaty et al., 2011) illustrates this point. In the three examples below we worked up data that separates out the amounts of succession classes allowing the reader to see where management work might need to happen (we do not provide prescriptions for what should be done-that is for local managers and stakeholders to do).



Departure from reference conditions can be caused by (A) increases in uncharacteristic vegetation, as in Great Basin Salt Desert Scrub, (B) increases in closed canopy successional classes, as in Ozark Oak Woodland, or (C) increases in early successional classes, as in Cascades Western Hemlock Forest. These vegetation changes are the expected outcomes of biological invasion, fire suppression, and logging, respectively.

How do we get the amounts of the succession classes for each ecosystem?

We need reference and current amounts of each succession class for each ecosystem. Where do those come from? From www.landfire.gov . 😄

  • Reference amounts come from state and transition models. Each “state” is a succession class and the transitions represent succession and disturbances. For LANDFIRE all disturbances are “natural” (e.g., fire, wind, flooding). To learn way more about this go to https://thenatureconservancy.github.io/landfiremodels/index.html.

For our work here we will use the refCon200.csv (path to file is “rawData/refCon200.csv”) file to get reference conditions.

For our work here we will use the combine200s.csv (path to file is “rawData/combine200s”) dataset.

BTW: what is all of this “200” business? It refers to the most recent LANDFIRE dataset.

OK I have the two input datasets needed to calculate VDEP-now what?

In general data prep, then visualization. More specifically:

Data prep with the reference dataset

This dataset is not “Tidy”. What does Tidy mean? It means that a dataset follows these 3 rules:

  1. Each variable must have its own column.
  2. Each observation must have its own row.
  3. Each value must have its own cell.

You need to figure out what is going on with the reference data and fix it. Here’s what you need to do:

  1. read (.csv) data
  2. view the data
  3. pivot longer so that the columns A-E are in one column named “sClass”, and the values are in a column named “refPercent”